A Potential Anti-prion Drug With 'Unprecedented' Potency

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A Potential Anti-prion Drug With 'Unprecedented' Potency

The urgent search for a medication to treat prion diseases has led scientists in Germany to synthesize a new group of compounds, including one that is 15 times more potent than an approved drug now being tested in clinical trials.



Their report is scheduled for the Nov. 2 issue of the biweekly ACS Journal of Medicinal Chemistry.

Prions are infectious proteins that cause brain disorders like Mad Cow Disease and Creutzfeldt-Jakob Disease (CJD) in humans. Peter Gmeiner and colleagues note that the recent emergence of a new form of CDJ, linked to consumption of infected beef mainly in Great Britain, intensified the search for anti-prion compounds.

Most potential drugs have proved ineffective, often because they could not enter brain tissue where prions reside. One promising drug, however, is in clinical trials. That drug is quinacrine, already approved for several other medical conditions.

Gmeiner's group describes the chemical synthesis and early laboratory testing of a family of anti-prion compounds that cross into brain tissue and combat prions. One of those compounds has what the report describes as "unprecedented" anti-prion activity, with 15 times greater potency than quinacrine.

http://www.sciencedaily.com/releases...1030120759.htm


J. Med. Chem., 49 (22), 6591 -6595, 2006. 10.1021/jm060773j S0022-2623(06)00773-4
Web Release Date: September 29, 2006

Copyright © 2006 American Chemical Society
A Chimeric Ligand Approach Leading to Potent Antiprion Active Acridine Derivatives: Design, Synthesis, and Biological Investigations

Silke Dollinger, Stefan Löber, Ralf Klingenstein, Carsten Korth, and Peter Gmeiner*

Department of Medicinal Chemistry, Emil Fischer Center, Friedrich-Alexander University, Schuhstrasse 19, D-91052 Erlangen, Germany, and Institute for Neuropathology, Medical School, Heinrich Heine University Duesseldorf, Moorenstrasse 5, D-40225 Duesseldorf, Germany

Received June 29, 2006

Abstract:

Human transmissible neurodegenerations including Creutzfeldt-Jakob disease are unique, since they are caused by prions, an infectious agent that replicates without nucleic acids but instead by inducing conversion of a host-resident normal prion protein to a misfolded conformational isoform. For pharmacotherapy of these unusual diseases, tricyclic heterocyclic compounds such as quinacrine have been considered, but with ambiguous success in vivo, so far. On the basis of the synergistic antiprion effects of quinacrine and iminodibenzyl derivatives, we introduce a novel class of potential pharmaceuticals representing structural chimeras of quinacrine and imipramine analogues. We describe the chemical synthesis and bioassays of a focused library of these compounds. The most potent target compound 2a revealed an EC50 value of 20 nM determined with a cell model of prion disease, thus substantially improving the antiprion efficacy of quinacrine.



http://pubs.acs.org/cgi-bin/abstract...jm060773j.html



Introduction

Prion diseases are transmissible neurodegenerative diseases

of humans and animals.1 The prion agent replicates without a

nucleic acid-encoded genome by converting host-resident normal

prion protein (PrPC)a to a pathogenic and infectious conformational

isoform PrPSc. Human prion diseases such as the most

prevalent Creutzfeldt-Jakob disease (CJD) are rare diseases that

cansuniquelysbe of sporadic, genetic, or infectious origin.

Animal prion diseases are almost exclusively infectious in origin

in the form of scrapie of sheep, bovine spongiform encephalopathy

(BSE) or mad cow disease of cattle, or chronic wasting

disease of American mule deer or elk. The emergence of a new

strain of human prions causing variant CJD (vCJD) through

the consumption of BSE-contaminated material 2 led to 160

deaths, primarily in Great Britain, and to concerns of an epidemy

of vCJD which, so far, has neither happened nor been

completely excluded.3 The new vCJD strain has different

characteristics, such as the occurrence of infectivity in blood

and peripheral organs, which increases the risk of horizontal

transmission, for example, during blood transfusions.4 These

issues have led to a focus on pharmacotherapeutic options of

prion diseases both for symptomatic, curative, and prophylactic

purposes or for decontamination of blood and transplanted

organs.

Although screening for antiprion compounds in scrapieinfected

mouse neuroblastoma cells (ScN2a) as a cell culture

model of prion disease has led to the identification of many

antiprion compounds, most of them proved to be ineffective

when applied to experimentally prion-infected rodents owing

to the lack of blood-brain barrier (BBB) permeability or

toxicity.5 The identification of BBB-permeable heterocyclic

compounds sparked a tremendous effort to enter clinical trials

applying the approved drug quinacrine to patients with CJD.6

Since animal experiments with quinacrine gave only modest or

ambiguous results,7 quinacrine pharmacotherapy could be

improved by introducing a combination of antiprion drugs.8

Structural modifications employing quinacrine as a lead compound

revealed that bis-acridines augmented antiprion activity

around 10-fold in vitro,9 but poor solubility is likely to limit

their in vivo use. The synergistic antiprion effects of quinacrineand

iminodibenzyl-derived antidepressants have prompted us

to synthesize heterodimers incorporating both recognition elements

with a piperazine unit,10 which is known as a privileged

substructure in a great number of bioactive agents, as the linking

element.

On the basis of preliminary investigations on the hybrid 1

(Figure 1) displaying a 5-fold improved antiprion potency over

quinacrine,8 we herein describe a novel class of antiprion agents

of type 2 defined by covalently linked acridine and iminodibenzyl

moieties and variations of the particular molecular

subunits. SAR studies led to the discovery of the iminodibenzyl

derivative 2a as the most active antiprion compound yet

described.

Chemistry. ...SNIP...FULL TEXT ;



http://pubs.acs.org/cgi-bin/sample.c.../jm060773j.pdf



TSS

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quinacrine has failed to ever cure anyone from cjd, and one side effect seems to be to turn the person taking the substance yellow. maybe this new cocktail will prove to be benificial. we can only hope so. ...TSS